There are known various types of filters for use in agricultural, domestic and industrial applications. One particularly successful type of filter is the disc filter, which is exemplified in the following patents and patent applications of the present applicant: U.S. Pat. Nos. 4,026,806; 4,045,345; 4,067,812; 4,207,181; U.S. patent application Nos. 623,353; 647,093; 647,094; Israel Patent Application No. 71674, and European Patent Application No. 85630236.9.
Another type of filter, known as the screen filter, is also known and comprises a cylindrical screen through which a liquid passes during filtration. The screen filter is characterized by the ability to provide extremely fine filtration, down to 50 microns or less.